The present invention relates to plastic closures for use on bottles or like containers, and specifically to a closure provided with a breakaway band as a tamper evident feature. The tamper evident feature is preferably used with a closure having a plurality of formations for preventing the container from backing-off of the closure when the container and closure are in a closed position.
Various configurations of tamper-evident container closures are known in which a frangible band breaks away from the closure upon opening. The band is connected to the closure by a number of relatively thin, easily severable bridges or pads. The closure is threaded upon the container finish or neck. An inner bead on the band engages a radially projecting locking ring on the container finish. Upon the initial opening of the container, the bridges sever and the band remains on the container finish.
A common problem with such closures is that the tamper evident band must be flexible enough to ride over the locking ring during application of the closure upon the container, yet be rigid enough to be retained upon the finish once the closure is initially opened to indicate tampering. At the same time, in order to minimize production costs, such tamper evident bands are optimally made of a minimal amount of plastic.
In many designs of breakaway bands, upon application of the closure to the container, a significant amount of frictional interference is generated between the band and the locking ring. This interference has been the bridges to collapse, forcing the band to contact the closure skirt. In other cases, the interference causes the bridge formations to sever, and the breakaway band to tuck upward between the closure skirt and the container neck, distorting the shape of the band and impairing its tamper evident effectiveness.
One attempt at solving this problem has been to thicken portions of the breakaway band for structural support in withstanding the above-identified frictional interference. However, a significant disadvantage of this solution is that the amount of material per cap increases, thus increasing the production costs as well as the shipping weight.
In addition to breakaway bands, molded plastic containers of the type employing a threaded closure member, such as bottles, jars, or the like normally include a smooth integral thread formed on the neck portion of the container. When a closure having a corresponding thread is tightened upon the smooth thread of the molded plastic container, there is a tendency for the closure to become loose. This loosening of the closure, commonly known as "backing-off", is due in part to vibration incurred during shipping and handling, to the self-lubricating qualities of the plastic materials normally used in molding the closures and containers, as well as to the tendency of such materials to flow or creep under stress, thereby permitting the closure to work itself off to relieve the stress set up in the threads due to tightening of the closure on the container. Backing-off can be a significant problem to packagers, in that containers having closures which are loose or appear to have been opened are less apt to be selected by consumers for fear of tampering and/or contamination.
Thus, it is an object of the present invention to provide a closure with a breakaway band which is configured to prevent unwanted misalignment or tucking.
It is a further object of the present invention to provide a closure with a tamper evident breakaway band which is lightweight, yet has sufficient support to withstand friction generated when the closure is applied upon the container neck.
It is another object of the present invention to provide a closure with back-off resistance, as well as with a tamper evident breakaway band.
Yet another object of the present invention is to provide a back-off resistant closure for a container having laterally projecting locking formations, the closure having formations which matingly engage the locking formations of the container surface to prevent the backing-off of the closure therefrom.